170 F. Sclimidt and T. R. Jones on 



may be an IsocMlina, as the margin extends around the 

 ventral border, and there is no inverted plate to be seen ; but 

 the valve is highest at the anterior part and not along the 

 ventral border, as I have shown to be the case with L. grandis. 



^^ Barrande himsclfj in describing the left valve of L. 

 gigantea^ sent to him by F. Romer (Syst. Silur. Boheme, 

 vol. i. suppl. p. 535), says, ' Limbo aplati, rclativemcnt large 

 aux deux bouts de la valve et disparaissant presque complcte- 

 ment vers le milieu du contour ventral, sur plus d'lm quart 

 de la longueur. Ce Ihnbe est endommage sur une partie du 

 contour de Lep. gigantea^ ct nous I'avons restaure dans la 

 region mediane :' pi. 34. figs. 4-(). That restoration, how- 

 ever, was not correct. The real form of the ventral border 

 you will find in F. Romer's original woodcut (Zeitschrift d. 

 deutsch. geol. Gesell. 1858, p. 356), exactly corresponding 

 to the specimen which I saw in the Breslau Museum. M. 

 Barrande himself is now entirely of my opinion with regard 

 to the genus of L. gigantea or grandis. 



" 3. As to your English specimens of L. halthica and L. 

 Hisingerij it would be difficult to identify them with ours, as 

 your Lejyerditia'. apparently are scarce and not well preserved. 

 With us, and in Scandinavia (and, it seems to me, in North 

 America also), the Lcpcrditioi occur abundantly in Upper- 

 Silurian strata, and appear to be very well adapted for charac- 

 terizing the different stages, as they do not pass from one 

 geological horizon to another, like some Trilobites and Brachio- 

 pods. Now let me try to revicAV the Leperditiai from the 

 Baltic Provinces, Scandinavia, and England, described in 

 your last ' Notes,' as far as possible for me to do. 



" Your fig. 1, pi. xix., may be the actual L. halthica of 

 Hisinger. Figs. 2 and 13 I willingly accept as the types of 

 L. halthica, var. contracfa, Jones. Figs. 3 and 4 are doubtful 

 forms. Fig. 5 [L. Hisingeri ?] seems very near to, if not 

 identical with, our L. Keyserlingi (see my fig. 34), corre- 

 sponding also in geological position. Fig. 6 \L. Hisingeri, 

 var. graciUnta, Jones] 1 Avould like to regard as intermecHate 

 to L.jjhascolus (His.), as defined by Kolmodin, and my L. 

 tyraica, both of which occur in the Uppermost Silurian. 

 Both L. j/haseolus [L. Angelini, Schmidt), with us and in 

 Gothland, and L. tyraica, on the Dniester in Galizia and 

 Podolia, have the characteristic angular spot around the eye- 

 tubercle, separated by a narrow space from the central (mus- 

 cular) spot (see my figs. 11 and 13), and may be regarded as 

 mere local varieties. Your fig. 14 [L. halthica, var. contracfa'}, 

 from Kamenetz-Podalsk, will be the true L. tyraica, as other 

 forms do not exist in that country. I studied the Dniester 

 Silurians, in 1872, at that place ; and Prof. Alth of Krakow 



